Fuel tank valve structure for a hybrid vehicle

Abstract

A fuel tank valve structure for controlling emission gas in a hybrid vehicle, comprising: a housing (10), one side of which is connected to a fuel tank and the other side of which is connected to a canister, a check valve (20) for opening or closing the housing (10) connected to the canister, a solenoid valve (30) connected to the check valve (20) for adjusting the internal pressure in the fuel tank to open or close the check valve (20), a fuel limiting vent valve device (40) connected to the end portion of the housing (10) connected to the fuel tank, and a pressure relief valve (50) connected to that lower end of the housing (10) which is connected to the canister, the check valve (20) comprising: a check valve rubber (21) with an opening (22) in the center, from which the emission gas in the fuel tank is selectively retained, a check valve body (23) mounted in contact with one side of the check valve rubber (21), and a check valve spring (24) arranged inside the check valve body (23) and providing elasticity to the check valve rubber (21).

Description

[0001] The present invention relates to a fuel tank valve structure for hybrid vehicles, of which the emission gas can be controlled under different driving and stopping conditions of plug-in hybrid vehicles (also called plug-in hybrid vehicles).

[0002] Hybrid vehicles, which are generally known or known from the related technology, are powered by energy from an internal combustion engine and energy from an electric motor, so they are of interest due to fuel savings and environmentally friendly properties.

[0003] However, because these vehicles are equipped with both an internal combustion engine and an electric motor to generate power, the weight of the vehicles increases, electrical energy is required to operate the electric motor, and power output is reduced. Furthermore, energy is lost during the process of converting and storing electrical energy.

[0004] Therefore, plug-in hybrid vehicles, which can be operated by charging the vehicle battery at common houses, have been developed using an internal combustion engine and an electric motor as independent power sources, making the best use of electric vehicles with reduced energy loss during the process of energy conversion in the vehicles, and using an efficient internal combustion engine that has been used in the related art.

[0005] Since the drive type changes with increasing drive share from electric motors in plug-in hybrid vehicles, emissions increase as a result of the reduction in the drive share of the internal combustion engine, so measures to combat this problem are necessary.

[0006] A fuel limiting vent valve device as in Fig. 1, for controlling emission gas and determining the refilling amount when refilling vehicles, has the function of enabling refilling by supplying air and emission gas contained in the fuel tank into the canister during refilling, the function of controlling the amount of fuel introduction by stopping the supply of gas from the fuel tank to the canister when the fuel tank is completely filled with fuel, and in addition the function of preventing fuel in the canister from overflowing therefrom or fuel leaking from the fuel tank.

[0007] The information disclosed in the above section is provided only to facilitate understanding of the general background of the invention and does not constitute prior art already known to a person of ordinary skill in the art.

[0008] For example, from JP 2004 - 68 738 A, a fuel tank valve structure for controlling emission gas in a vehicle is known, the fuel tank valve structure comprising: a housing, one side of which is connected to a fuel tank and the other side of which is connected to a canister, a check valve for opening / closing the housing connected to the canister, a solenoid valve connected to the check valve for adjusting the internal pressure in the fuel tank to open / close the check valve, a fuel limiting vent valve device connected to the end portion of the housing connected to the fuel tank, and a pressure relief valve connected to the lower end of the housing connected to the canister.

[0009] Another device for treating vaporized fuel is known from US 7 152 587 B2.

[0010] Furthermore, a fuel vapor recovery system is known from US 5 647 334 A.

[0011] In addition, a device for detecting anomalies in a fuel system is known from US 6 557 401 B2.

[0012] Furthermore, a ventilation device in a fuel tank is known from US 2006 / 0 231 138 A1.

[0013] In addition, a fuel tank pressure control valve is known from US 6 843 271 B2 and US 6 612 338 B2.

[0014] Also known from US 2006 / 0 185 652 A1 is a control valve for controlling fuel vapor, the control valve comprising: a housing, one side of which is connected to a fuel tank and the other side of which is connected to a canister, a check valve for opening / closing the housing connected to the canister, and a solenoid valve connected to the check valve for adjusting the internal pressure in the fuel tank for opening / closing the check valve, an additional pressure relief valve being provided separately.

[0015] Various aspects of the present invention are directed to providing a fuel tank valve structure for hybrid vehicles, which can control the emission gas when the engine is operating, and at the same time prevent emission gas from flowing into the canister when the amount of emission gas in the fuel tank increases when the engine is stopped due to excessive / frequent operation of the electric motor, such as in plug-in hybrid vehicles.

[0016] The present invention provides fuel tank valve structures according to claims 1 and 5. Further embodiments of the respective fuel tank valve structures are described in the dependent claims.

[0017] According to one aspect of the invention, the fuel tank valve structure for controlling the emission gas in a hybrid vehicle comprises a housing, one side of which is connected to a fuel tank and the other side of which is connected to a canister, a check valve disposed in the housing for opening or closing a first fluid passage between the canister and the fuel tank, a solenoid valve device selectively coupled to the check valve for opening or closing the first fluid passage for adjusting the internal pressure of the fuel tank, a fuel limiting vent valve device mounted on the housing and selectively fluidly connected to a space formed in the housing between the check valve and the fuel limiting vent valve device, and a pressure relief valve.which is attached to the housing and from which the fuel tank and the canister are selectively fluidly connected via a second fluid passage.

[0018] The check valve comprises: a check valve rubber slidably installed in the housing and having an opening in its center, of which the first fluid passage is selectively closed and the emission gas is retained in the fuel tank, a check valve body fixed to one side of the check valve rubber, and a check valve spring disposed in the housing and biasing the check valve rubber to provide elasticity in one direction.

[0019] The solenoid valve may include: a solenoid valve housing, a rod selectively communicating with the opening of the check valve rubber, a valve stem projecting outwardly and connected to the other end portion of the rod for movement with the rod, a core disposed in the solenoid valve housing at a predetermined distance from the valve stem and selectively in close contact with the end portion of the valve stem, and a coil wound around the valve stem and the core for actuating the valve stem.

[0020] A solenoid valve O-ring may be arranged around the front end of the solenoid valve body, and a core O-ring may be arranged around the rear end of the core so that leakage of emission gas is prevented, and a valve tappet stopper may be arranged on the core so that noise and vibration generated by contact with the valve tappet are reduced.

[0021] The pressure relief valve may include: a pressure relief valve housing connected to the housing to form the second fluid passage with the canister, a vacuum vent valve disposed on one side of the pressure relief valve housing for adjusting the internal pressure in the fuel tank to open the second fluid passage when the internal pressure in the fuel tank is lower than the pressure in the pressure relief valve housing, a pressure relief valve body displaceable in the pressure relief valve housing by the internal pressure to open the second fluid passage, and a pressure relief valve spring disposed in the pressure relief valve housing and biasing the pressure relief valve body in one direction to selectively open the first fluid passage.

[0022] According to the exemplary embodiments of the invention, it is possible to adjust the capacity of fuel tanks used in the related art and supply emission gas to the canister.

[0023] Furthermore, it is possible to freely control the supply of emission gas to the canister even when the engine of a hybrid vehicle is operating or not, and it is possible to adjust the supply of emission gas from registered fuel, thereby improving stability and user friendliness.

[0024] Furthermore, it is possible to easily release pressure due to normal pressure and negative pressure in the fuel tank.

[0025] Further advantages and features of the subject matter according to the present invention will become apparent from the following detailed description with reference to the accompanying drawings, which serve to further explain certain principles of the present invention.

[0026] The invention is explained in more detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 is a cross-sectional view of a fuel tank valve structure according to the related art; Fig. 2 is a cross-sectional view of a fuel tank valve structure according to an exemplary embodiment of the invention; Fig. 3a and Fig. 3b each shows a perspective external view of an exemplary embodiment of the invention; Fig. 4 is a cross-sectional view of a housing and check valve used in the present invention; Fig. 5 is a cross-sectional view of a solenoid valve used in the present invention; Fig. 6 is a cross-sectional view of a pressure relief valve used in the present invention; Fig. 7 is a cross-sectional view of a fuel limiting vent valve device used in the present invention; Fig. 8 is a cross-sectional view of a portion of the fuel tank valve structure according to an exemplary embodiment of the invention; Fig. 9a to Fig. 9c are functional diagrams illustrating the operation of the check valve and the solenoid valve according to the present invention; Fig. 10a to Fig. 10c Functional diagrams illustrating the operation of the pressure relief valve according to the present invention; Fig. 11 is a perspective view of another exemplary embodiment of the invention.

[0027] Embodiments of the present invention are explained in more detail below with reference to the drawings.

[0028] In the figures of the drawing, identical or similar parts are designated by the same reference numerals.

[0029] As from Fig. 2, a valve structure used in a fuel tank according to an exemplary embodiment of the invention includes: a housing 10 having one side connected to the fuel tank and the other side connected to a canister; a check valve 20 disposed in the housing 10 for opening / closing the housing 10 connected to the canister; a solenoid valve 30 coupled to the check valve 20 and opening / closing to adjust the internal pressure of the fuel tank; a fuel limit vent valve device 40 connected to that end of the housing 10 connected to the fuel tank; and a pressure relief valve 50 connected to that lower end of the housing 10 connected to the canister.

[0030] That is, the present invention supplies and collects the generated emission gas from the fuel tank to the canister, and particularly securely controls the amount of increasing emission gas when the engine operates less due to the electric motor operation of the plug-in hybrid vehicle.

[0031] As from Fig. 4, for this operation the housing 10 is connected to the top of the fuel tank by fixing the housing 10 to the fuel tank by means of a cover 11, a collar 12 being provided which prevents emission gas leakage by sealing the space between the housing 10 and the fuel tank.

[0032] As further shown by the Fig. 3A and Fig. 3B, a separate nipple 13 is attached to the outside of the housing 10 so that fuel can be prevented from overflowing from the canister or leaking from the fuel tank.

[0033] The check valve 20 is arranged in the connecting region of the housing 10 and the canister and comprises a check valve rubber 21 having an opening 22 in the center, by which the emission gas in the fuel tank is retained, a check valve body 23 which is fixed in contact with one side of the check valve rubber 21, and a check valve spring 24 which is arranged inside the check valve body 23 and by which elasticity is imparted to the check valve rubber 21.

[0034] Since the check valve 20 is arranged in the housing 10 for selectively discharging the emission gas through the first fluid passage 100, from which the fuel tank and the canister are connected, as shown in Fig. 4, the emission gas flowing from the fuel tank through the casing 10 into the canister cannot easily leak out because of the check valve rubber 21 having a circular plate shape, and it is possible to adjust the pressure and amount of the discharged emission gas due to the action of the check valve body 23 and the check valve spring 24.

[0035] The check valve body 23 is fixed to one side of the check valve rubber 21 and has a plurality of leg portions extending from the side for supporting the check valve 23 on the housing 10, and the spring arranged in the check valve body 23 imparts elasticity to the check valve body 23 so that the check valve 20 opens at a corresponding pressure.

[0036] The solenoid valve 30 is arranged on one side of the housing 10 and comprises a solenoid valve housing 31, a rod 32, one end portion of which can make contact with one side of the check valve rubber 21 in a space 60, a valve stem 33 which projects outwardly and is connected to the other end portion of the rod 32 for movement with the rod 32, a core 34 which is arranged separately from the valve stem 33 and has an inwardly formed recess which is designed to provide close contact with the end portion of the valve stem 33, and a coil 35 which is wound around the valve stem 33 and the core 34.

[0037] As from Fig. 5, the outer shape of the solenoid valve 30 is defined by a cylindrical solenoid valve housing 31, and the rod 32 is in contact with the check valve 20, whereby it is possible to adjust the internal pressure of the fuel tank and discharge the emission gas together with the check valve 20.

[0038] Since the spring is arranged around the rod 32, it is possible for the rod 32 to obtain elasticity and easily adjust the opening / closing.

[0039] The valve stem 33 connected to one end portion of the rod 32 has a generally cylindrical shape, with the other unconnected end of the rod 32 projecting outward.

[0040] The core 34 is formed at a predetermined distance from the side of the valve stem 33 and has the inwardly formed recess formed to provide close contact with the end portion of the valve stem 33 so as to provide a space in which the valve stem 33 can move rightward and leftward.

[0041] As further stated in Fig. 8, a solenoid valve O-ring 36 is arranged around the front end of the solenoid valve housing 31 and a core O-ring 37 is arranged around the rear end of the core 34 such that the O-rings are in tight contact between the solenoid valve 30 and the housing 10 and the core 34 and solenoid valve housing 31, and thus can be prevented from escaping emission gas to the outside.

[0042] Further, a valve tappet stopper 38 is formed in the center of the recess of the core 34, so that it is possible to reduce noise and vibration generated when the core 34 and the valve tappet 33 contact each other while the valve tappet 33 moves right and left when the valve tappet 33 is operated.

[0043] Preferably, the valve stem stopper 38 is arranged in the center where, in accordance with the shape of the protruding end portion of the valve stem 33 and the recess of the core 34, the protruding end portion of the valve stem 33 contacts the core 34. Preferably, the valve stem stopper 38 is made of rubber to absorb the impact.

[0044] In Fig. 6 shows a pressure relief valve 50 used in an exemplary embodiment of the invention, the pressure relief valve 50 comprising: a pressure relief valve housing 51 connected to the lower end of the housing 10, a pressure relief valve O-ring 52 disposed in the pressure relief valve housing 51 to maintain airtightness, a vacuum vent valve 53 disposed on one side of the pressure relief valve housing 51 for adjusting pressure by selectively opening the second fluid passage 200 connecting the fuel tank and the canister, a pressure relief valve body 55 disposed in the pressure relief valve housing 51 and sliding up and down for adjusting pressure by selectively opening the second fluid passage 200 connecting the fuel tank and the canister, a pressure relief valve rubber 56 connected to the pressure relief valve body 55, and a pressure relief valve spring 54.which is connected to the inside of the pressure relief valve body 55 and the housing 10 to provide elasticity.

[0045] The pressure relief valve housing 51, which is connected to the lower end of the housing 10, preferably has an elliptical cross-section, and the pressure relief valve O-ring 52 is preferably arranged along the inside of the pressure relief valve housing 51 to maintain airtightness between the pressure relief valve 50 and the housing 10.

[0046] The vacuum vent valve 53 is formed on one side of the lower portion of the relief valve housing 51 and can be tightened or opened (e.g., expanded) according to the internal pressure of the fuel tank. The relief valve body 55 is arranged to move up and down inside the relief valve housing 51 and can selectively open the second fluid passage 200 connecting the fuel tank and the canister according to the internal pressure of the fuel tank.

[0047] In a similar shape to the vacuum vent valve 53, the relief valve rubber 56 is formed under the lower portion of the relief valve body 55. The relief valve spring 54 is arranged at one end in the relief valve body 55 and supported at the other end on the inside of the housing 10, so that the relief valve body 55 is provided with elasticity.

[0048] Out of Fig. 7 shows a fuel limiting vent valve device 40 used in an exemplary embodiment of the invention, the fuel limiting vent valve device 40 comprising a cylindrical fuel limiting vent valve housing 41, a guide 42 movable up and down in the fuel limiting vent valve housing 41, a rubber seal 43 and a sealing plate 44 arranged in the guide 42 for adjusting the emission gas flow, a float 45 connected to the lower end of the guide 42 and movable up and down by the surface buoyancy of the fuel, and a fuel limiting vent valve spring 46.

[0049] The fuel limit vent valve device 40 collects and delivers generated emission gas from the fuel tank to the canister, similar to the fuel limit vent valves used in the related art. The fuel limit vent valve device 40 is normally open to deliver emission gas to the canister. However, when the fuel tank is completely filled with fuel, the fuel causes the float 45 to rise, closing the interior of the fuel limit vent valve device 40, temporarily increasing the internal pressure of the fuel tank and stopping fuel injected from a refilling gun.

[0050] From the Fig. 9a to 9c illustrate the operation of the check valve 20 and the solenoid valve 30 used in an exemplary embodiment of the invention.

[0051] When a plug-in hybrid vehicle is driven or stopped only by motors, without using the machine (ie without an internal combustion engine) and no fuel is supplied, the solenoid valve 30 is not actuated and accordingly the solenoid valve 30 and the check valve 20 are connected to each other, as shown in Fig. 9a, whereby the housing 10 is sealed.

[0052] Accordingly, the fuel tank valve structure is fully closed, in which only an OPR (pressure relief function) function is performed at a pressure above a reference value inside the fuel tank.

[0053] Thereafter, when a plug-in hybrid vehicle operates the machine or is filled, the solenoid valve is actuated, and accordingly, the valve stem 33 in the solenoid valve 30 is moved into close contact with the core 34 and the rod 32 is moved to the right accordingly, as shown in Fig. 9b.

[0054] Thus, a gap is created between the rod 32 and the check valve 20 and the emission gas can flow through the opening 22 in the center of the check valve rubber 21, so that it is possible to adjust the pressure between the fuel tank and the canister.

[0055] This means that through the initial operation, the internal pressure in the fuel tank can be reduced first, and when the pressure is suddenly dropped, malfunction of a valve in the fuel tank can be prevented, thereby maintaining the safety of the whole vehicle.

[0056] From the Fig. 10a to 10c illustrate the operation of the pressure relief valve 50 used in an exemplary embodiment of the invention.

[0057] In Fig. 10a shows a pressure relief valve 50 at an internal pressure in the fuel tank of 0 to 33 kPa, i.e., at normal pressure. At normal pressure, the vacuum vent valve 53 maintains a stable balance, and the pressure in the up-and-down directions between the pressure relief valve body 55 and the pressure relief valve spring 54, which are arranged at the lower portion of the pressure relief valve housing 51, is balanced.

[0058] How Fig. 10b, when the internal pressure of the fuel tank exceeds 33kPa, that is, when there is overpressure, the relief valve body 55 and the relief valve rubber 56 are moved to an upper portion of the relief valve housing 51 and the relief valve spring 54 is compressed, so that emission gas flows from the inside of the fuel tank through the relief valve 50 into the canister.

[0059] How Fig. 10c, flows when the internal pressure of the fuel tank is low, ie when negative pressure prevails, the emission gas flows from the canister into the fuel tank through the side of the negative pressure vent valve 53 so that pressure equilibrium can be established.

[0060] In the Fig. 3a and Fig. In the exemplary embodiment shown in Fig. 3b, the housing 10 is connected or combined with the fuel tank, which is made of steel, and in Fig. 11 illustrates a connecting structure of a fuel tank made of plastic according to another exemplary embodiment.

[0061] That is, in the Fig. 3a and Fig. In the exemplary embodiment shown in Fig. 3b, the housing 10 is connected to the fuel tank made of steel by means of the cover 11, wherein the cover 11 is fastened to the fuel tank by means of bolts or screws.

[0062] In the Fig. However, in the exemplary embodiment shown in Fig. 11, the assembly is preferably manufactured by injection molding using a low-pass structure, and preferably, the housing 10 for connecting the housing 10 to the fuel tank, which is made of plastic, is manufactured by injecting POM, and the connecting portion 14 is manufactured by insert molding HDPE around the housing 10.

[0063] According to the exemplary embodiment described above, it is possible to adjust the capacity of existing fuel tanks, supply emission gas to the canister, prevent the emission gas from being supplied from the fuel tank to the canister when the engine is stopped, and supply emission gas from the fuel tank to the canister when the engine is operating.

[0064] Furthermore, it is possible to discharge emission gas from the fuel tank to the canister, and it is also possible to release pressure in the event of overpressure and underpressure in the fuel tank, even when the engine is not running and no fuel is injected.

[0065] To facilitate the explanation of the teachings underlying the invention, the terms "upper", "lower", "inner" and "outer" are used to describe the features of the exemplary embodiment with reference to their position as they appear to the viewer of the drawing.

Claims

[1] A fuel tank valve structure for controlling the emission gas in a hybrid vehicle, comprising: a housing (10), one side of which is connected to a fuel tank and the other side of which is connected to a canister, a check valve (20) for opening or closing the housing (10) connected to the canister, a solenoid valve (30) connected to the check valve (20) for adjusting the internal pressure in the fuel tank to open or close the check valve (20), a fuel limiting vent valve device (40) connected to the end portion of the housing (10) connected to the fuel tank, and a pressure relief valve (50) connected to that lower end of the housing (10) which is connected to the canister, the check valve (20) comprising: a check valve rubber (21) with an opening (22) in the center, from which the emission gas in the fuel tank is selectively retained, a check valve body (23) mounted in contact with one side of the check valve rubber (21), and a check valve spring (24) arranged inside the check valve body (23) and providing elasticity to the check valve rubber (21). [2] A fuel tank valve structure according to claim 1, wherein the solenoid valve (30) comprises: a solenoid valve housing (31), a rod (32) selectively connected to the opening (22) and the check valve rubber (21), a valve stem (33) projecting outwardly and connected to the other side of the rod (32) for movement with the rod (32), a core (34) which is separate from the valve stem (33) and has an inwardly formed recess for close contact with the end portion of the valve stem (33), and a coil (35) wound around the valve stem (33) and the core (34). [3] A fuel tank valve structure according to claim 2, wherein a solenoid valve O-ring (36) is disposed around the front end of the solenoid valve housing (31) and a core O-ring (37) is disposed around the rear end of the core (34) so as to prevent leakage of emission gas, and wherein a valve stem stopper (38) is formed in the center of the recess of the core (34) so as to reduce noise and vibration generated by contacting with the valve stem (33). [4] Fuel tank valve structure according to one of claims 1 to 3, wherein the pressure relief valve (50) comprises: a pressure relief valve housing (51) connected to a lower end of the housing (10), a pressure relief valve O-ring (52) designed to maintain airtightness in the pressure relief valve housing (51), a vacuum vent valve (53) arranged for adjusting pressure on one side of the pressure relief valve housing (51), a pressure relief valve body (55) which is arranged to slide up and down in the pressure relief valve housing (51), a pressure relief valve rubber (56) connected to the pressure relief valve body (55), and a pressure relief valve spring (54) coupled to the inside of the pressure relief valve body (55) and the housing (10) to provide elasticity. [5] A fuel tank valve structure for controlling the emission gas in a hybrid vehicle, comprising: a housing (10), one side of which is connected to a fuel tank and the other side of which is connected to a canister, a check valve (20) arranged in the housing (10) for opening or closing a first fluid passage (100) between the canister and the fuel tank, a solenoid valve device selectively connected to the check valve (20) for adjusting the internal pressure of the fuel tank to open or close the first fluid passage (100), a fuel limiting vent valve device (40) mounted on the housing (10) and selectively fluidly connected to a space (60) formed in the housing (10) between the check valve (20) and the fuel limiting vent valve device (40), and a pressure relief valve (50) mounted on the housing (10) and from which the fuel tank and the canister are selectively fluidly connected via a second fluid passage (200), the check valve (20) comprising: a check valve rubber (21) slidably mounted in the housing (10) and having an opening (22) in its center, by which the first fluid passage (100) is selectively closed and the emission gas is retained in the fuel tank, a check valve body (23) attached to one side of the check valve rubber (21), and a check valve spring (24) which is arranged in the housing (10) inside the check valve body (23) and which prestresses the check valve rubber (21) to provide elasticity in one direction. [6] A fuel tank valve structure according to claim 5, wherein the solenoid valve (30) comprises: a solenoid valve housing (31), a rod (32) which is selectively connected to the opening (22) of the check valve rubber (21), a valve stem (33) projecting outwardly and connected to the other end portion of the rod (32) for movement with the rod (32), a core (34) arranged in the solenoid valve housing (31) at a predetermined distance from the valve stem (33) and capable of selectively making close contact with the end portion of the valve stem (33), and a coil (35) wound around the valve tappet (33) and the core (34) to actuate the valve tappet (33). [7] A fuel tank valve structure according to claim 6, wherein a solenoid valve O-ring (36) is arranged around the front end of the solenoid valve housing (31) and a core O-ring (37) is arranged around the rear end of the core (34) so as to prevent leakage of emission gas, and wherein a valve tappet stopper (38) is arranged on the core (34) by means of which noise and vibration generated by contacting with the valve tappet (33) are reduced. [8] Fuel tank valve structure according to one of claims 5 to 7, wherein the pressure relief valve (50) comprises: a pressure relief valve housing (51) connected to the housing (10) to form the second fluid passage (200) with the canister, a vacuum vent valve (53) arranged on one side of the pressure relief valve housing (51) for opening the second fluid passage (200) for adjusting the internal pressure in the fuel tank when the internal pressure in the fuel tank is lower than the pressure in the pressure relief valve housing (51), a pressure relief valve body (55) which is arranged to be displaceable by the internal pressure in the pressure relief valve housing (51) to open the second fluid passage (200), and a pressure relief valve spring (54) disposed in the pressure relief valve housing (51) and biasing the pressure relief valve body (55) in one direction for selectively opening the second fluid passage (200). [9] A fuel tank valve structure according to claim 8, further comprising: a pressure relief valve rubber (56) connected to the pressure relief valve body (55), and a pressure relief valve O-ring (52) arranged in the pressure relief valve housing (51) to maintain airtightness.

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